On Mon, 6 Jun 2005, Jamie Guinan wrote:
> > That's odd. While I'm not familiar with the details of OHCI or the
> > LH7A404 driver, normally a host controller driver does not check the port
> > status when communicating with a device. Port status is checked
> > asynchronously by the hub driver. Of course, there could be something
> > going on here that I'm unaware of...
>
> Well, it may not be as a direct result of the scsi read(). From my logs
> it looks like the call stack leading up to this point was,
>
> rh_report_status()
> ohci_hub_status_data()
> roothub_portstatus()
>
> The only reference to rh_report_status I can find is,
>
> static int rh_status_urb (struct usb_hcd *hcd, struct urb *urb)
> ...
> hcd->rh_timer.function = rh_report_status;
>
> I don't want to speculate on the call stack before that, as I didn't
> keep track of thread context while logging.
Okay, that's what I expected. That routine gets called four times per
second, regardless of what else is going on.
> > > 2) Does the 0x30101 look like a sane response? I'm seeing 0x30100
> > > when I remove an IOGEAR media reader connected through via a
> > > standard USB TypeA port.
> >
> > It means that for some reason the host controller thought the device
> > disconnected momentarily and then reconnected. In the IOGEAR case you
> > didn't reconnect; hence the different code.
>
> Ok, I'll test the IOGEAR with a quick {dis,re}-connect.
You'll have to be pretty quick -- less than 1/4 second. Such a test won't
tell you very much; if you do it right you'll see the 0x30101 code instead
of 0x30100. Nothing more. It's not worthwhile.
The important point is that, owing to some hardware peculiarity (board
layout problem?), the D+ pull-up on the USB device was disconnected
briefly from the bus. Maybe that will give you hint where to look.
> > Nothing wrong with doing it that way, except that you might prefer to use
> > the debugfs filesystem instead of procfs. That's what it's intended for.
>
> Ok, I'll try that.
Don't take my comment too seriously. For your own debugging purposes you
can use whatever filesystem you like and nobody will care -- it's a free
country. It would matter only if you intended to distribute your
debugging code (which I assume you do not).
Alan Stern
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